elixir_ale v1.2.1 ElixirALE.SPI View Source

This module enables Elixir programs to interact with hardware that’s connected via a SPI bus.

Link to this section Summary

Functions

Returns a specification to start this module under a supervisor

Return a list of available SPI bus device names. If nothing is returned, it’s possible that the kernel driver for that SPI bus is not enabled or the kernel’s device tree is not configured. On Raspbian, run raspi-config and look in the advanced options

init(arg)

Invoked when the server is started. start_link/3 or start/3 will block until it returns

release(pid)

Stop the GenServer and release the SPI resources

start_link(devname, spi_opts \\ [], opts \\ [])

Start and link a SPI GenServer

transfer(pid, data)

Perform a SPI transfer. The data should be a binary containing the bytes to send. Since SPI transfers simultaneously send and receive, the return value will be a binary of the same length or an error

Link to this section Types

spi_option()

spi_option() ::
  {:mode, 0..3}
  | {:bits_per_word, 0..16}
  | {:speed_hz, pos_integer()}
  | {:delay_us, non_neg_integer()}

Link to this section Functions

child_spec(arg)

Returns a specification to start this module under a supervisor.

See Supervisor.

device_names()

device_names() :: [String.t()]

iex> ElixirALE.SPI.device_names
["spidev0.0", "spidev0.1"]

init(arg)

Invoked when the server is started. start_link/3 or start/3 will block until it returns.

args is the argument term (second argument) passed to start_link/3.

Returning {:ok, state} will cause start_link/3 to return {:ok, pid} and the process to enter its loop.

Returning {:ok, state, timeout} is similar to {:ok, state} except handle_info(:timeout, state) will be called after timeout milliseconds if no messages are received within the timeout.

Returning {:ok, state, :hibernate} is similar to {:ok, state} except the process is hibernated before entering the loop. See c:handle_call/3 for more information on hibernation.

Returning {:ok, state, {:continue, continue}} is similar to {:ok, state} except that immediately after entering the loop the c:handle_continue/2 callback will be invoked with the value continue as first argument.

Returning :ignore will cause start_link/3 to return :ignore and the process will exit normally without entering the loop or calling c:terminate/2. If used when part of a supervision tree the parent supervisor will not fail to start nor immediately try to restart the GenServer. The remainder of the supervision tree will be started and so the GenServer should not be required by other processes. It can be started later with Supervisor.restart_child/2 as the child specification is saved in the parent supervisor. The main use cases for this are:

The GenServer is disabled by configuration but might be enabled later.
An error occurred and it will be handled by a different mechanism than the Supervisor. Likely this approach involves calling Supervisor.restart_child/2 after a delay to attempt a restart.

Returning {:stop, reason} will cause start_link/3 to return {:error, reason} and the process to exit with reason reason without entering the loop or calling c:terminate/2.

Callback implementation for GenServer.init/1.

release(pid)

release(GenServer.server()) :: :ok

Stop the GenServer and release the SPI resources.

start_link(devname, spi_opts \\ [], opts \\ [])

start_link(binary(), [spi_option()], [term()]) :: GenServer.on_start()

Start and link a SPI GenServer.

SPI bus options include:

mode: This specifies the clock polarity and phase to use. (0)
bits_per_word: bits per word on the bus (8)
speed_hz: bus speed (1000000)
delay_us: delay between transaction (10)

Parameters:

devname is the Linux device name for the bus (e.g., “spidev0.0”)
spi_opts is a keyword list to configure the bus
opts are any options to pass to GenServer.start_link

transfer(pid, data)

transfer(GenServer.server(), binary()) :: binary() | {:error, term()}